Table 1.

Demographic and clinical characteristics of the patients in our study^a.

Characteristic	No. (%)
	Arthritis-irAEa, n = 20	Osteoarthritis, n = 4	No-irAEs, n = 9
Median age (range)	56.5 years	60.5 years	62 years
	(34–77)	(57–64)	(47–77)
Male	14 (70)	2 (50)	5 (56)
Median BMI (range)	28.7	31.2	30.8
	(21.7–37.9)	(29.6–31.6)	(22.4–33.7)
Tumor type
Melanoma	11 (55)	1 (25)	6 (67)
RCC	4 (20)	0 (0)	0 (0)
NSCLC	4 (20)	1 (25)	3 (33)
Neuroendocrine	1 (5)	2 (50)	0 (0)
ICI(s)
Nivolumab	6 (30)	N/A	6 (67)
Pembrolizumab	4 (20)	N/A	1 (11)
Durvalumab	1 (5)	N/A	1 (11)
Ipilimumab + nivolumab	6 (30)	N/A	1 (11)
Ipilimumab + pembrolizumab	3 (15)	N/A	0 (0)
CTCAEc grade II–IV irAEs prior to the arthritis
Colitis	7 (35)	N/A	N/A
Dermatitis	4 (20)	N/A	N/A
Myocarditis	1 (5)	N/A	N/A
Type I diabetes mellitus	1 (5)	N/A	N/A
Hypothyroidism	1 (5)	N/A	N/A
Neuritis	1 (5)	N/A	N/A
Pattern of arthritis
Undifferentiated monoarthritis	3 (15)	N/A	N/A
Undifferentiated oligoarthritis	13 (65)	N/A	N/A
Undifferentiated polyarthritis	4 (20)	N/A	N/A
Median time from first ICI infusion to development of arthritis (range)	35.5 weeks	N/A	N/A
	(0.5–365)
Stopped ICI therapy before development of arthritis	6 (30)	N/A	N/A
Colitis-irAE	1 (5)	N/A	N/A
Myocarditis-irAE	1 (5)	N/A	N/A
Neuritis-irAE	1 (5)	N/A	N/A
Tumor progression	2 (10)	N/A	N/A
Completion of ICI therapy	2 (10)	N/A	N/A
Arthritis-irAE CTCAE grade		N/A	N/A
II	16 (80)	N/A	N/A
III	4 (20)	N/A	N/A
Median CDAId (range)	21.5 (7–60)	N/A	N/A
Median ESRe (range)	53 mm/h	8 mm/h	N/A
	(8–108)	(7–9)
Median CRPf (range)	80.0 mg/L	3.5 mg/L	N/A
	(2.0–300)	(1.3–5.8)
ANA-positiveg	3 (16)	N/A	N/A
RF-positive	2 (10)	N/A	N/A
Anti-CCP antibody–positiveg	0 (0)	N/A	N/A
HLA B27-positiveg	1 (5)	N/A	N/A

^aAbbreviations: irAEs immune-related adverse events, BMI body mass index, RCC renal cell carcinoma, NSCLC non-small cell lung carcinoma, ICI immune checkpoint inhibitor, N/A not applicable, CTCAE common terminology criteria for adverse events, CDAI clinical disease activity index, ESR erythrocyte sedimentation rate, CRP C-reactive protein, ANA anti-nuclear antibody, RF rheumatoid factor, CCP cyclic citrullinated peptide.

^bOther cancers included ovarian cancer (n = 1), breast cancer (n = 2), glioblastoma (n = 1), cervical cancer (n = 1), and neuroendocrine tumor (n = 1).

^cCTCAE grades range from I to V, with higher values indicating more severe.

^dValues of CDAI range from 0 to 76, with higher values indicating more active inflammatory arthritis.

^eNormal values of ESR range from 0 to 20 mm/h.

^fNormal values of CRP range from 0 to 10 mg/L.

^gn = 19 in the arthritis-irAE group.